Dean, your Dad's knife is the same as my Dad's was. However, they are the Russell (now Grohmann) #3 Boat Knife. Thy are also referred to as "jump knife" by military guys who often got them, as well as Yachtsman Knife in the boating community. I read somewhere the name boat knife came from the triangular handle resembling the shape of a boat. I can't vouch for that. What I do know is that the military still gives #3s out as recognition because I saw one for sale today that had lettering and logo on it to recognize those who were part of the Kandahar Mission.
The more popular, and iconic is the Russell Belt Knife, though they are both regarded as very comfortable knives.
Sent from my Pixel 6 using Tapatalk